JP2825898B2 - Laminated film for packaging - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a laminated film for packaging, and more specifically, it is transparent and inexpensive without impairing gas barrier properties even when subjected to hot water treatment. The present invention relates to a laminated film for packaging.

In the present invention, packaging is a concept including both primary packaging for directly packaging contents and secondary packaging for storing contents in a plastic bag or container and further packaging the bag or container. is there.

[Conventional technology and problems to be solved]

The gas barrier property of a packaging film after hot water (high-pressure steam) treatment is important in the food and medical fields.

For example, in the packaging of retort food, the food is stored in a packaging bag using a film having a high gas barrier property, and this is subjected to retort treatment.However, when the gas barrier property of the packaging film is impaired during the retort treatment and thereafter. Food cannot be stored for a long time, and the original significance of packaging is lost.

In general, when packaging medical liquids such as physiological saline and Ringer's solution, they are stored in a plastic container or the like to form a primary package, and the primary package is placed in, for example, an autoclave, and the hot water is placed in the autoclave. A method of sterilizing by leaving it under high-pressure steam for about 30 minutes is employed. In this case, the container is not handled bare, and the subsequent secondary packaging is performed under aseptic conditions. However, this operation is complicated and not preferable. In some cases, the primary packaged product is secondarily packaged and sterilized directly in this packaged state.

Also in the secondary packaging film in such a case, the gas barrier property, particularly the oxygen gas barrier property of the packaging film at the time of the sterilization treatment and thereafter is important, as described above.

Conventionally, packaging using aluminum foil has been used as a packaging material that can be subjected to hot water treatment and has excellent gas barrier properties, but such packaging materials have excellent hot water resistance and gas barrier properties, but contain contents. However, they have the disadvantage that they are not visible from the outside and are expensive.

Inexpensive packaging materials that can be treated with hot water and have excellent transparency include polyester, polyamide, and polyvinylidene chloride, all of which have gas barrier properties as compared with those using aluminum foil. Has the disadvantage of being low. On the other hand, a resin such as a saponified ethylene-vinyl acetate copolymer has a high gas barrier property, but is highly dependent on humidity, and has a tendency to significantly increase oxygen permeability in a high humidity region.

Therefore, in general, the gas barrier property of the packaging structure is maintained by coating and laminating with a protective layer such as polyethylene having a low water absorption. However, under high-humidity and high-temperature conditions such as in retort treatment, the water absorption of polyethylene itself protecting the gas barrier resin layer increases, so that the moisture permeating the protection layer moves to the gas barrier resin layer, There is a disadvantage that the gas barrier properties as a packaging film is significantly impaired.

Furthermore, recently, a plastic film is provided with one or more drive plating layers of silicon or silicon oxide on the surface thereof, and a film printed thereon as required, and a polyolefin film. And a packaging material for retort pouches, which are laminated via a polyurethane adhesive (JP-A-62-103139).
issue). However, this packaging material has a drawback that the gas barrier performance after the hot water treatment is insufficient and cannot be used for contents requiring a high degree of gas barrier properties.

[Means for solving the problem]

In view of the above circumstances, the present inventors have conducted intensive studies and as a result, if a specific film having a silicon oxide thin film on its surface is bonded to and protected by a specific film, hot water (high-pressure steam) treatment is performed. It has been found that the gas barrier properties are maintained at a high level without impairing the gas barrier properties, and the present invention has been completed.

That is, the gist of the present invention comprises a first layer (A), a second layer (B), and a third layer (C) defined as follows:
The laminated film for packaging is characterized in that the second layer is joined to one surface of the first layer and the third layer is joined to the other surface of the second layer.

(A) The first layer (A) is a transparent laminated plastic film having a transparent silicon oxide thin film on at least one side of a transparent plastic film having a collection rate of 1% or less after a hot water treatment at 120 ° C. for 30 minutes. It consists of at least one transparent film.

(B) The second layer (B) has a shrinkage rate of 1% or less after being treated with hot water at 120 ° C. for 30 minutes, and conforms to JIS Z0208.
It consists of a transparent plastic film having a measured value of moisture permeability at 60 ° C. and 90% RH of 60 g / m ² · 24H or less.

(C) The third layer (C) is made of a transparent plastic film having a tack strength of not more than 10 g / 15 mm after hot water treatment at 120 ° C. for 30 minutes and being heat sealable.

[Action]

The silicon oxide thin film of the first layer (A) exhibits a high gas barrier property. The transparent plastic film of the first layer (A) does not largely shrink during hot water treatment due to its low shrinkage property, and as a result, does not give cracks to the silicon oxide thin film formed on its surface. .

The transparent plastic film of the second layer (B) exhibits the same action as described above due to its low shrinkage property, and also protects the silicon oxide thin film from water during hot water treatment due to its moisture permeability resistance.

The low tack strength of the transparent plastic film of the third layer (C) prevents the films from sticking to each other, keeps the appearance beautiful, and facilitates handling.

 Hereinafter, the present invention will be described in detail.

The laminated film for packaging of the present invention comprises a first layer (A), a second layer (B) and a third layer (C) as defined above, and is provided on one surface of the first layer (A). The second layer (B) is configured by joining the third layer (C) to the other surface.

 First, each of the above layers will be sequentially described.

(1) First Layer (A) In the laminated film for packaging according to the present invention, the first layer (A) is at least one side of a transparent plastic film having a shrinkage of 1% or less after treatment with hot water at 120 ° C. for 30 minutes. A transparent silicon oxide thin film (hereinafter abbreviated as “SO thin film”).

The above-mentioned low shrinkage transparent plastic film is not particularly limited, and various transparent plastic films can be used.Of course, an unstretched film may be used, but a stretched film is used from the viewpoint of mechanical strength and the like. A balanced type biaxially oriented polyester film is used.

The biaxially stretched polyester film excels not only in mechanical strength, but also in heat resistance and transparency, and is heat-set after stretching, and then vertically and horizontally relaxed. Shrink films are commercially available. In addition, even a normal-grade film can be used by leaving it in a heating oven at about 200 ° C. for several hours and shrinking it sufficiently before use.

In the present invention, the shrinkage after the hot water treatment at 120 ° C. for 30 minutes means the shrinkage in the vertical and horizontal directions (area shrinkage).

SO formed on low shrinkage transparent plastic film surface
The thin film may be formed on one side of the film or on both sides.

The SO thin film can be formed by using silicon monoxide, silicon dioxide, a mixture thereof, or the like as a deposition material by any of a vacuum deposition method, a sputtering method, and an ion plating method. In addition, a reactive vapor deposition method in which silicon, silicon monoxide, silicon dioxide, a mixture thereof, or the like is used as a vapor deposition material while supplying oxygen gas can be employed.

Prior to the formation of the SO thin film, it is also possible to use an anchor coat agent to increase the adhesive strength between the thin film and the film. Suitable anchor coating agents include an isocyanate-based, polyethyleneimine-based, and organic titanium-based adhesion promoter and a polyurethane polyester-based adhesive. Further, as the anchor coating agent, a non-solvent type adhesive of polyethylene type, polyester type or polyamide type may be used.

If the SO thin film is 10% by weight or less, even if calcium, magnesium or their oxides are mixed therein as impurities, an extreme decrease in the gas barrier performance of the intended packaging film is recognized. Absent.

The thickness of the SO thin film is preferably selected in the range of 100 to 5000 mm. If the thickness of the SO thin film is less than 100 mm, the gas barrier performance is insufficient, and if it exceeds 5000 mm, curling occurs in the film, which causes problems, and the transparent thin film itself tends to crack or peel. Not preferred.

The first layer (A) may be a single-layer body composed of a single transparent laminated film having a transparent SO thin film on one side of the low-shrinkage transparent plastic film, or a transparent adhesive film composed of two or more transparent laminated films. It may be either a laminate joined using an agent or a laminate obtained by joining a transparent laminated film and a transparent plastic film using a transparent adhesive. In this case, examples of the adhesive that can be used include urethane-based, acrylic-based, and polyester-based adhesives.

(2) Second Layer (B) In the present invention, the second layer (B) is joined to one surface of the first layer (A), preferably to the surface on the SO thin film side.

The second layer (B) functions as a protective layer, has a shrinkage rate of 1% or less after a hot water treatment at 120 ° C. for 30 minutes, and has a moisture permeability at 40 ° C. and 90% RH according to JIS Z 0208. of the measured value is 60g / m ² · 24
It consists of a transparent plastic film of H or less.

Such a transparent plastic film is not particularly limited as in the case of the first layer (A), and various transparent plastic films can be used. However, from the viewpoint of hot water shrinkage, the transparent layer of the first layer (A) can be used. Since the biaxially stretched polyester film selected as the plastic film has a sufficiently small moisture permeability, the same biaxially stretched polyester film as that of the first layer (A) is preferably used in the second layer (B). You. Of course, similarly to the first layer (A), an unstretched film can be used, and examples thereof include a polypropylene film. For example, “FH” manufactured by Nimura Chemical Co., Ltd.
Χ ”(general grade) can be used as it is as a transparent plastic film for the second layer (B) of the present invention.

Since the moisture permeability of the second layer (B) varies depending on the film thickness used, the thickness is appropriately determined according to the type of plastic.

The definition of the heat shrinkage rate in the second layer (B) is the first layer
This is the same as in the case of the layer (A).

(3) Third Layer (C) In the present invention, the third layer (C) is bonded to the other surface of the first layer (A), preferably to the surface on the side of the low-shrinkage transparent plastic film.

The third layer (C) functions as a sealant,
It is made of a transparent plastic film that has a tack strength of 10 g / 15 mm or less after hot water treatment for 0 minutes and is heat sealable.

The tack strength in the present invention means the tack (adhesion) strength of the third layer (C). And since the tack strength is determined by heat resistance, the third layer (C) has high heat resistance,
Moreover, it must be a heat-sealable transparent plastic film.

A typical example of a transparent plastic film suitable for such purpose is a heat-resistant grade unstretched polypropylene film.

Various types of heat-resistant polypropylene films are commercially available. For example, Tokyo Cellophane Co., Ltd.
"R @ C-7", "R @ C-11" and the like can be preferably used. Even if a transparent plastic film having a high tack strength is used, a film whose surface is roughened to reduce the tack strength can be used in the same manner.

Next, a laminated structure in which the respective layers are joined will be described.

When joining the second layer (B) and the third layer (C) to the first layer (A) surface, a dry lamination method using a urethane-based adhesive, an acrylic-based adhesive, a polyester-based adhesive, or the like is used. A known method such as a lamination method can be employed. The order of lamination of the third layer (C) may be before or after the formation of the SO thin film of the first layer (A).

The third layer (C) can be formed by extrusion coating on the first layer (A), preferably on the surface of the low-shrink transparent plastic film, without using an adhesive.

Depending on the contents to be packaged, the packaging film requires ultraviolet blocking ability in addition to gas barrier performance, but the packaging film according to the present invention can impart ultraviolet blocking performance as needed.

For example, a packaging film having an ultraviolet blocking ability can be obtained by adding a substance having an ultraviolet absorbing ability to the adhesive layer at the time of joining the above layers. As the ultraviolet absorber to be used, one or a combination of commercially available ultraviolet absorbers such as benzophenone and benzotriazole are used, and the amount of the ultraviolet absorber used is determined depending on the required ultraviolet absorbing ability. It is needless to say that the ultraviolet ray blocking ability can be imparted also by using a layer formed of a material having an ultraviolet absorbing ability as the layer (A) to (C) forming film.

In the laminated film for packaging according to the present invention, the total thickness of the second layer (B) and the third layer (C) is preferably in the range of 5 to 400 μm, and the total thickness is strength, flexibility. The thickness is preferably in the range of 50 to 500 μm, more preferably 100 to 300 μm, from the viewpoint of economy and the like. The ratio (A) :( B) :( C) of the thickness of each layer excluding the adhesive layer is 1: 1 to 10:
It is preferably from 1 to 10.

In order to adjust the overall thickness between the first layer (A) and the second layer (B) or between the first layer and the third layer (C),
A transparent plastic film can be interposed. The plastic film to be interposed is not particularly limited as long as it is transparent, but the same type of plastic film as that forming the second layer (B) is preferably used. The thickness of the interposed plastic film is selected in relation to the thickness of the entire laminated film.

The laminated film for packaging of the present invention is used with the second layer (B) positioned so as to be exposed on the surface, and is used for primary packaging,
It can be suitably used for any of secondary packaging. In particular, when used for secondary packaging, the third layer (C), which functions as a sealant, has a low tack strength property, as well as a high gas barrier property, so that the peelability from the primary packaging container is excellent, and therefore, the handling property is good. It is.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist.

In the following examples, each property value was measured by the following method. The thickness of the silicon oxide transparent thin film layer was measured by a quartz crystal film thickness meter.

(1) hot water shrinkage (%): film a sample was cut out of 100mmφ from, after heating in hot water at 120 ° C. 30 min in an autoclave, extraction, the outer diameter was measured 10 points, the minimum value D _{Min .} to. The hot water shrinkage is calculated from the following equation.

(2) Moisture permeability (gr / m ² · 24H) of the film: conforms to JIS Z 0208. A 100 × 100 mm three-side sealed bag is made from a predetermined film, and granular anhydrous chloride is used as a moisture absorbent in the bag. After filling with 30 gr of calcium, the remaining one side is sealed to obtain a sample. Each of the samples was 10 ° C. × 40 ° C.
The film was placed in an atmosphere of 90% RH, and the moisture permeability of the film was determined from the change in weight.

(3) Tack strength (g / 15mm): Cut out 140 × 140mm □ sample from film
After heat sealing the other side, the remaining one side was vacuum-sealed to form a bag having an inner size of 120 to 120 mm. The bag was heated in hot water at 120 ° C. for 30 minutes by an autoclave, taken out, and a seal portion on four sides was cut out to obtain a 120 × 120 mm sample in which two films were overlapped. A 15 mm x 120 mm tangled sample was cut out from this sample, and the adhesive strength of the two films was measured.

(4) Oxygen ^{permeability: (cc / m 2 · 24H} · atm) using Modern Control Co. OX-TRAN 100 type oxygen permeability measuring apparatus, temperature 30 ° C., was measured at 80% relative humidity conditions.

The oxygen permeability was measured before and after the measurement of the hot water shrinkage.

(5) Film transparency (%): The light transmittance of the film in visible light was measured using a spectrophotometer manufactured by Hitachi, Ltd., and the light transmittance at 550 nm was defined as the transparency of the film.

(6) Peelability: In the measurement of tack strength, the peelability of a sample consisting of two films that overlapped each other was evaluated.

Example 1 A biaxially stretched polyethylene terephthalate film (stretching magnification: 3 × 3 times, thickness: 12 μm, hot water shrinkage: 0.9%) was supplied to a vacuum evaporation apparatus, and electron beam was conducted under a vacuum of 5 × 10 ⁻⁵ Torr. By heating, 99.9% of silicon monoxide was heated and evaporated in order to obtain a transparent laminated plastic film having a transparent thin film layer of silicon oxide of 1000 ° formed on one side of the film (first layer). A biaxially stretched polyethylene terephthalate film (moisture permeability 60 gr / m ² · 24H) “(second layer)” was applied to the silicon oxide thin film side of the obtained film using a urethane-based adhesive (Takelac A606 and Takenate A manufactured by Takeda Pharmaceutical Co., Ltd.). -9 and a 2-component adhesive in a ratio of 9: 1) (thickness: 2 μm), and further, on the opposite side of this layer as a sealant layer, the same urethane-based adhesive as above is used. Stretched film (thickness 50μ, tack strength 8gr / 15mm) (third
To form a three-layer transparent plastic film.

The physical properties of the obtained laminated film were measured, and the results are shown in Table 1.

Further, as Examples 2 to 6 and Comparative Examples 1 to 6, a laminated film was prepared in the same manner as in Example 1 except that the type, thickness, and number of transparent films of each layer were changed as shown in Table 1. The measurement results such as physical properties of the laminated film are shown in Table 1. (However, the measurement results of the light transmittance were 83% in each case.
As described above, they have sufficient transparency, and therefore, the description in Table 1 is omitted).

In Example 3 in which two films were used as the first layer (A), the transparent laminated plastic film of Example 1 in which a transparent thin film layer of silicon oxide was formed on one side of the film was used.
As a first layer (A), a laminate is used in which one transparent laminated plastic film is bonded to the silicon oxide thin film side and the other transparent laminated plastic film is bonded to the film side using a urethane adhesive. .

 In Table 1, the meanings of the abbreviations are as follows.

[PET]

Biaxially stretched polyethylene terephthalate film (drawing ratio 3 × 3 times) [Heat-resistant CPP] Unstretched polypropylene film (Heat-resistant grade) [General CPP] Unstretched polypropylene film (General grade) [ONY] Biaxially stretched nylon-6 film (Stretched) [OPP] Biaxially stretched polypropylene film (drawing ratio 3 × 3) [Effect of the Invention] The above-described laminated film for packaging of the present invention maintains its inherently excellent gas barrier properties even when subjected to hot water (high-pressure steam) treatment, is transparent and inexpensive, and is used for secondary packaging. The peelability, which is important when used, is also good.

Therefore, the value of the packaging film of the present invention is great as a packaging film for contents accompanied by hot water treatment (retort treatment, sterilization treatment) in the food and medical fields.

Continuation of the front page (56) References JP-A-3-71832 (JP, A) JP-A-63-164950 (JP, A) JP-A-63-162238 (JP, A) (58) Fields studied (Int .Cl. ⁶ , DB name) B32B 1/00-35/00

Claims (3)

(57) [Claims] 1. A first layer (A) and a second layer (A) defined as follows:
It comprises a layer (B) and a third layer (C), wherein the second layer is joined to one surface of the first layer, and the third layer is joined to the other surface of the first layer. Laminated film for packaging. (A) The first layer (A) has a small number of transparent laminated plastic films having a transparent silicon oxide thin film on at least one side of a transparent plastic film having a shrinkage rate of 1% or less after a hot water treatment at 120 ° C. for 30 minutes. And a transparent film containing one layer. (B) The second layer (B) has a shrinkage rate of 1% or less after being treated with hot water at 120 ° C. for 30 minutes, and conforms to JIS Z0208.
It consists of a transparent plastic film having a measured value of moisture permeability at 60 ° C. and 90% RH of 60 g / m ² · 24H or less. (C) The third layer (C) is made of a transparent plastic film having a tack strength of not more than 10 g / 15 mm after hot water treatment at 120 ° C. for 30 minutes and being heat sealable. 2. The laminated film for packaging according to claim 1, wherein the second layer (B) is joined to the surface of the first layer (A) on the silicon oxide thin film side. 3. The thickness of the silicon oxide thin film of the first layer (A) is
2. The method according to claim 1, wherein the angle is in the range of 100 to 5,000 mm.
Item 3. The laminated film for packaging according to item 2 or 2.